1. Field of the Invention
The present invention relates to a forklift provided with a driving wheel capable of being steered by 360°.
2. Description of the Related Art
There is conventionally provided a seat-riding reach type forklift 21, which will be referred to as a forklift hereinafter, shown in FIG. 6. In the forklift 21, an operator sits on a seat 22. While operating a steering wheel 25 with his left hand, the operator operates a directional switch 23 shown in FIG. 7 with his right hand so as to control the direction of movement (i.e., running or proceeding direction) of the forklift 21. When the operator adjusts an amount of pressure on the accelerator foot pedal arranged on a floor 26 of the forklift 21, the running speed of the forklift 21 can be controlled.
In this forklift 21, there is a type in which a steering angle of the driving wheel 24 is restricted by a stopper so that the steering angle can be in a range ±90° with respect to the front of the forklift 21. Alternatively, there is a type in which the stopper is not provided, and the driving wheel 24 is configured so that it can be steered in a 360° range. In the former case, the rotary direction of the running motor for driving the driving wheel 24 is primarily determined by the position of the directional switch 23. For example, when the directional switch 23 is positioned, or tilted, toward the operator's side, the running motor is normally rotated, and the forklift 21 advances forward. In the latter case, it is possible to apply the structure of the former case, and the rotary direction of the running motor for driving the driving wheel 24 is primarily determined by the tilting position of the directional switch 23.
FIGS. 8 to 12 are views showing a state of the forklift 21 in which the operator gradually turns the steering wheel 25. It should be noted that the forklift 21 is drawn in a simplified manner in FIGS. 8 to 12. In FIGS. 8 to 12, two triangles express the directional switch 23, and one of the triangles, which is painted out black, means that the directional switch 23 has a position in which it is tilted to this black triangle side. When the directional switch 23 is tilted to the front side of the forklift 21, that is, when the directional switch 23 is tilted to the front side of the operator, the running motor is normally rotated, so that the driving wheel is normally rotated, i.e., the driving wheel undergoes a forward rotation so that the forklift is driven in a forward direction. When the directional switch 23 is tilted to the rear side of the forklift 21, that is, when the directional switch 23 is tilted to the rear side of the operator, the running motor is reversely rotated, so that the driving wheel 24 is reversely rotated, i.e. the forklift is driven in a rearward direction.
FIG. 8 is a view showing a state in which the driving wheel 24 is normally rotated and the steering angle is 0° with respect to the front direction of the forklift 21. As shown by the arrow in the drawing, the forklift 21 proceeds straight. FIG. 9 is a view showing a state in which the driving wheel 24 is normally rotated and the steering angle is −45° with respect to the front direction of the forklift 21. As shown by the arrow in the drawing, the forklift 21 proceeds diagonally to the right by 45°. FIG. 10 is a view showing a state in which the driving wheel 24 is normally rotated and the steering angle is −90° with respect to the front direction of the forklift 21. As shown by the arrow in the drawing, the forklift 21 is driven toward the right so as to revolve around the intermediate point of the two idler wheels 27a, 27b which are arranged at the rear. FIG. 11 is a view showing a state in which the driving wheel 24 is normally rotated and the steering angle is −135° with respect to the front direction of the forklift 21. As shown by the arrow in the drawing, the forklift 21 reverses diagonally to the right. FIG. 12 is a view showing a state in which the driving wheel 24 is normally rotated and the steering angle is −180° with respect to the front direction of the forklift 21. As shown by the arrow in the drawing, the forklift undergoes a rearward straight movement.
In this forklift 21, the driving wheel 24 of which can be steered by 360°, only by turning the steering wheel 25, the running direction of the forklift 21 can be freely changed. Therefore, this forklift 21 is advantageous in that the operability is higher than that of a forklift in which the steering angle of the driving wheel 24 is restricted by a stopper.
On the other hand, in order to ensure the safety of others in the immediate surroundings of the forklift during loading and unloading operations it is conventional that an audio warning is activated to indicate the running direction of the forklift. For example, in the case of a forklift in which the steering angle of the driving wheel 24 is restricted by the stopper and the rotary direction of the running motor is primarily determined by the position of the directional switch 23, when the directional switch 23 is positioned to tilt to the front direction of the forklift 21, that is, when the directional switch 23 is tilted to the front side of the operator, a chime indicating forward movement is sounded. On the other hand, when the directional switch 23 is tilted to the rear direction of the forklift 21, that is, when the directional switch 23 is tilted to the rear side of the operator, a buzzer indicating reverse movement is sounded.
In the case of the forklift 21 in which the driving wheel can be steered by 360°, in order to ensure safety of others during loading and unloading operations, it is necessary to inform those in the surrounding area of the direction of movement of the forklift 21. However, in this case, when the above warning method, which is performed only according to the tilted position of the directional switch 23, is adopted, the following problems may be encountered.
The tilting direction of the directional switch 23 shown in FIG. 8 is in the same state as that of the directional switch 23 shown in FIG. 12, and the rotary direction of the driving wheel 24 shown in FIG. 8 is the same as that of the driving wheel 24 shown in FIG. 12. However, the steering angle of the driving wheel 24 shown in FIG. 8 is different from that of the driving wheel 24 shown in FIG. 12 by 180°. Accordingly, the running direction of the forklift 21 shown in FIG. 8 is opposite to that of the forklift 21 shown in FIG. 12. In the case shown in FIG. 13, the tilted position of the directional switch 23 is opposite to that of the directional switch 23 shown in FIG. 8, and the rotary direction of the driving wheel 24 shown in FIG. 13 is opposite to that of the driving wheel 24 shown in FIG. 8. However, the steering angle of the driving wheel 24 shown in FIG. 13 is different from that of the driving wheel 24 shown in FIG. 8 by 180°. Therefore, the direction of movement of the forklift 21 shown in FIG. 13 is the same as that of the forklift 21 shown in FIG. 8. In the case shown in FIG. 14, the tilted position of the directional switch 23 is opposite to that of the directional switch 23 shown in FIG. 12, and the rotary direction of the driving wheel 24 shown in FIG. 14 is opposite to that of the driving wheel 24 shown in FIG. 12. However, the steering angle of the driving wheel 24 shown in FIG. 14 is different from that of the driving wheel 24 shown in FIG. 12 by 180°. Therefore, the direction of movement of the forklift 21 shown in FIG. 14 is the same as that of the forklift 21 shown in FIG. 12. That is, the following problematic cases may occur. While the directional switch 23 is tilted to the front side of the operator and the chime of forward movement is activated, the forklift 21 is actually moving in the rearward, i.e., reverse, direction. Further, while the directional switch 23 is tilted to the rear side of the operator and the reverse buzzer is activated, the forklift 21 is actually moving forward. Therefore, when workers in the surrounding area of the forklift 21 judge the direction of movement of the forklift 21 solely by the sound of the forward chime or the rearward buzzer, the workers in the surrounding area may be misinformed and make erroneous judgments concerning safety.
On the other hand, when the forklift 21 is started again, for example, after it has been once stopped in order to conduct a loading or unloading operation, or when the operator is replaced, in the case where the directional switch 23 is tilted to the front side of the operator, it is impossible for the operator to know which direction the forklift 21 is going to move when restarted. When the operator drives the forklift 21 while the direction of movement (i.e., running direction or proceeding direction) of the forklift 21 is unknown, the workers in the surrounding areas of the forklift 21 may be exposed to danger.
A conventional forklift is provided with direction indicating lamps which indicate which direction, i.e., right or left, the forklift will proceed, so that workers in the surrounding area of the forklift can determine which direction the forklift will move. When an operator manually operates a direction indicating lever, an indicating lamp turns on which corresponds to the direction of movement of the forklift. Concerning the direction indicating lever, there is a type of direction indicating lever capable of being manually returned to the neutral position from the right or the left indicating position. There is also a type of direction indicating lever capable of being automatically returned to the neutral position from the right or the left indicating position when a steering wheel is turned back by an angle not less than a predetermined angle. Such types of direction indicating levers are widely used.
On the other hand, a forklift is provided with a head lamp and rear lamp so that the forklift can run safely when the direction of movement is illuminated by the lamps. It is common that these head lamps and rear lamps are turned on and off when the operator manually operates a switch.
In this connection, a forklift moves (runs) in a direction to which the driving wheel is directed. However, there is provided a forklift, the driving wheel of which is capable of revolving by 360°. This forklift is capable of running in all directions. It is difficult for workers in the surrounding area of this forklift, the driving wheel of which is capable of revolving by 360°, to recognize which direction it will move. Accordingly, there is a possibility that the forklift runs in a direction which is not expected by the workers in the surrounding area of this forklift.
In order to solve the above problems, it is preferable for the operator to operate an indication lamp so that the workers in the surrounding area of the forklift can visually recognize the proceeding direction of the forklift. However, there is a possibility that the operator neglects his duty and drives the forklift without giving a signal of the proceeding direction of forklift. In this way, there is a possibility that the function of the indication lamp is not used even when the forklift is provided with the indication lamp.
On the other hand, for the forklift having a driving wheel which is capable of revolving by 360°, even when the rotary direction of the driving wheel is the same, the direction of movement of the forklift can be freely changed by revolving the driving wheel, and thus, an excellent operability can be realized by this type forklift.
However, in the case where a direction of movement of the forklift is changed by revolving the driving wheel from a state of forward movement, in which the head light is turned on, to a state of reverse movement, the forklift is reversing while the head lamp remains turned on. In order to solve the above problem, the operator must manually operate the switch to turn on and off the head light each time the direction of movement is changed. In this case, there is a possibility that the operator forgets to operate the switch. There is also a possibility that the time of operating the switch is delayed and the forklift continues to run as it is.